30 



CALIFORNIA ACADEMY OF SCIENCES. 



that time. A raised beach unconformable with the upper San Pedro strata at Dead- 

 man Island shows that there have been orographic movements since the upper San 

 Pedro beds were deposited. All of this evidence, then, leads to the conclusion that 

 there has been a sufficient lapse of time since the deposition of the upper San Pedro 

 strata, to admit of marked faunal and orographic changes. 



The upper San Pedro series is well developed on Los Cerritos Hill, where the 

 typical fossiliferous gravels of the upper San Pedro formation overlie unconformably 

 the brown, tilted sandstones which form the major portion of that hill. A little above 

 E (diagram E, Plate XXIII), the gravel stratum has a dip of 4° due south. Below 

 the gravel stratum is a thin bed of sand, which is also very fossiliferous. At G the 

 gravel stratum is only a few feet below the surface of the hill, but near the top of the 

 hill this stratum is covered by a deeper deposit of sands and sandy soil. The dip of 

 the stratum at K is N. 85° W. at an angle of from 12° to 15°. At K the gravel is 

 overlain by a depo.sit of fine, unfossiliferous sand four feet thick. 



At all the localities on Los Cerritos Hill where the upper San Pedro beds are 

 exposed, the underlying formation is a series of sands and conglomerates. No fossils 

 were obtained in the underlying series qf rocks, but they are probably of the lower 

 San Pedro series. 



It will be noticed, on looking at the contours on diagram E, Plate XXIII, and 

 observing the dips at the different places, that the dip of the gravel stratum conforms 

 very nearly to the slope of the hill. There is a fault at H, which cuts the upper San 

 Pedro stratum. The sand deposits above the gravels in a few places are probably 

 what is left of layers of sand which once covered the whole area. On the flanks of 

 the hill, both to the northwest, where the Los Angeles Terminal Railway cuts the 

 ridge, and toward the south, where the ocean has exposed the beds, sands overlie or 

 replace the gravel stratum. This fossiliferous upper San Pedro stratum is at no place 

 on Los Cerritos Hill more than a few feet thick. W. S. T. Smith' thinks that per- 

 haps this hill is wave built, but a careful examination shows that it is the result of 

 an orogenic movement which has taken place since the lower San Pedro beds were 

 deposited there. This is shown by the contortion of the lower formation, and by the 

 steep dips of the uppermost layers, which conform almost exactly with the slope of 

 the hill. This orogenic movement has taken place since the upper San Pedro series 

 was deposited, and is evidence in favor of the theory that the upper San Pedro beds 

 are at least older than the latest Pleistocene. 



List of Species Collected in the Upper San Pedro Beds at Los Cerritos. 



A tiijena cerritensis 

 Amifinlis caltoaa 

 A nr/iilus hutloni 

 Anomia lampe 

 A/itarU branneri 

 Cardium corbis 



PELECYPODA. 



Cardium datum 

 Cardium procerum 

 Cardium quadrigenarium 

 Chama exogyra 

 Ghama pellucida 

 Corbula luteola 



Cri/ptotnya californica 

 Donax litvigata 

 Clijeymeris harharensis 

 Glycymcris sepientrionalis 

 Hinnites giganteus 

 Lcevicardium substriatum 



' Topognpbic Slndy of the Iilanda of Southern California. I)y W. 8. T. Smith. Bull. Dept. Qeol.. Univ. of Cal., Vol. II, 



1900, p. 224. 



